The method for preparing highly purified halogen-free o-phthalaldehyde
For example the phthalaldehyde of Phthalyldicarboxaldehyde (OPA) can be used for a lot of fields, for example can be used as the intermediate of dyestuff, optical brightener or particular polymers, can be used for biotic pesticide or photograph industry, and is used for synthetic drug.Of many uses because of it, existing description to several different methods.Therefore, for example according to EP-B-0147593, Phthalyldicarboxaldehyde (OPA) can obtain by the following method: in methyl alcohol naphthalene is carried out ozone and decompose, and the superoxide that generates is carried out catalytic reduction, extract then or crystallization.The shortcoming of this method is to be difficult to formed ester as by product is separated with OPA, and separates also insufficient.
In addition, OPA is to heat and the unsettled reactive compounds of oxidation, and prolonged storage then is easy to caking, thereby makes the dissolution process required time longer, and this can cause the OPA decolouring.A kind of possible method that prevents the reaction that the aldehyde generation is not expected has been described: use the Phthalyldicarboxaldehyde tetraalkyl acetal for preparing by electrochemical oxidation among the EP-A1-0522312 as the storage compound.
EP-B-0839789 further discloses and has formed acetal by acid catalysis and distill subsequently OPA is changed into suitable storage compound, for example be converted into dialkoxyphthalan (dialkoxyphthalane) or tetraalkyl acetal, after acetal being decomposed fully, can obtain purity and surpass 99.5% thick OPA by acid hydrolysis.
Yet for example the thick OPA according to the EP-B-0839789 preparation is orange, also need carry out recrystallization again after with for example activated carbon or Tonsil decolouring.
The fusing point that obtains by crystallization is that 57 ℃ thin OPA powder is easy to into piece equally.And the shade and quality of different products in batches also there are differences.
US 5107032 discloses by the preparation tetrahalo-o-xylene and has prepared OPA 90-146 ℃ of following hydrolysis subsequently.This need come for example tetrachloro-o-Xylol of hydrolysis with sodium acetate in acetic acid aqueous solution under the highest 146 ℃ and 3.5bar, afterwards with toluene extraction 5 times, the organic phase that merges of distillation then obtains yield and be 87% OPA.But it is not halogen-containing that one of shortcoming of this method is that products obtained therefrom is not.
Therefore, the objective of the invention is to find improving one's methods of the highly purified Halogen OPA of preparation.
Unexpectedly, this purpose realizes by the following method: hydrolysis tetrahalo-o-xylene under greater than 155 ℃ high temperature, acetal turns to corresponding Phthalyldicarboxaldehyde acetal afterwards, comes the purifying acetal by distillation, decomposes acetal at pH under greater than 1.5 condition then.
Therefore, the present invention relates to prepare improving one's methods of highly purified halogen-free o-phthalaldehyde, it comprises:
A) under the pressure of 155-160 ℃ temperature and 2-5bar, suitably in the presence of phase-transfer catalyst, tetrahalo-o-xylene is hydrolyzed into Phthalyldicarboxaldehyde,
B) 0 to the temperature of reflux temperature, in acidity alcohol solution, Phthalyldicarboxaldehyde is converted into corresponding dialkoxyphthalan, then
C) under greater than 1.5 to 7 pH, by acid hydrolysis so that acetal decomposition obtains highly purified halogen-free o-phthalaldehyde.
Method of the present invention can prepare highly purified halogen-free o-phthalaldehyde.
Initiator is a tetrahalo-o-xylene.Suitable tetrahalo-o-xylene is the compound of following formula for example:
Wherein, X can be Cl, Br or I
Tetrahalo-o-xylene (THX) can also be replaced once or more times by suitable base alternatively.The example of suitable base is C
1-C
4Alkyl, C
5-C
20Aryl, OH, NO
2, CN, Cl, Br or CO
2H.The unsubstituted THX compound of preferred use, and X is preferably chlorine.Suitable THX compound can be buied (wherein X is Cl or Br) maybe can be with known method preparation, for example by under conditions of exposure or by means of for example AIBN, PCl
3Make o-Xylol and chlorine element reaction with the radical initiator of dibenzoyl peroxide etc.
According to the present invention, under the pressure of 155-160 ℃ temperature and the preferred 3-4bar of 2-5bar, THX is hydrolyzed to corresponding Phthalyldicarboxaldehyde.In the presence of alkali (for example NaOH, LiOH, KOH etc.), hydrolysis is by C
1-C
4Carry out in the Aquo System that carboxylic acid is formed.Preferably in the presence of NaOH (intensity 40-50%), use acetate.For this purpose, preferably carboxylic acid or moisture carboxylic acid are mixed with THX, add aqueous alkali and water then.Yet the order of interpolation also can change.The amount of used carboxylic acid is greater than 4 to 20 molar equivalents based on THX.Being preferably based on THX is the 8-10 molar equivalent.The amount of used alkali is the 4.0-5.0 molar equivalent based on THX.
In order to reach higher speed of reaction, can suitably in reaction mixture, add phase-transfer catalyst (PTC) (is 1-5mol% based on THX).Suitable PTC is that conventional for example quaternary ammonium salt is with the compound of quaternary alkylphosphonium salt, for example tetraalkylammonium salt and Si Wan Ji phosphonium salt or aralkyl trialkyl ammonium salts.Preferred salt is halide salt.Its example is tetrabutylammonium chloride or Tetrabutyl amonium bromide, ethyl trioctylphosphine phosphonium chloride, benzyltriethylammoinium chloride etc.
After hydrolysis takes place, obtain corresponding thick Phthalyldicarboxaldehyde (OPA), then solvent and extraction agent are distilled by extracting with for example conventional extraction agent of methyl tertiary butyl ether, toluene, ethyl acetate etc.
Subsequently, in step b),, in a usual manner thick OPA is changed into acetal, i.e. dialkoxyphthalan by carrying out the acid catalysis acetalation with alcohol.In the case, the alcohol of use is preferably C
1-C
4Alcohol, special particular methanol or ethanol.For this purpose, thick OPA is dissolved in alcohol.Transfer to 0-3, preferred 0.5-2 by adding sour pH then with solution.The example of suitable acid is for example HCl, H
2SO
4, H
3PO
4The organic acid or the acid ion exchangers of mineral acid, for example formic acid, acetate, tosic acid or methylsulfonic acid.The temperature of this step be 0 ℃ to reflux temperature, preferred 0 ℃ to 50 ℃.
After acetalation takes place, in solution, add aqueous alkali with neutralizing acid or acidic organic compound.The example of suitable alkali is NaOH or KOH.
Subsequently or simultaneously, remove alcohol by distillation as solvent.
Then, dialkoxyphthalan is separated with subsequently distillation by extraction.At this moment, the isolating OPA acetal of gained has high Halogen quality (>99.5GC area %) and very high yield (greater than 92%).
In step c), be similar to prior art, the decomposition of acetal takes place equally in a conventional manner by acid hydrolysis.According to the present invention, pH is greater than 1.5 to 7, preferred 1.6-2.5.
Used acid is similarly for example HCl, H
2SO
4, H
3PO
4The mineral acid or the organic acid of acetate, formic acid and tosic acid or methylsulfonic acid for example.Temperature of reaction is preferably between room temperature and 60 ℃.Pure and mild (in appropriate circumstances) acid of removing simultaneously, is steamed.Then, in appropriate circumstances, the OPA that obtains in this way can for example be further purified by extraction, washing or crystallization.
OPA by purification process gained of the present invention has high Halogen quality (>99.5GC area %) and very high yield (greater than 92%).And, come the OPA of purifying to present the fixed color according to the present invention, no longer need to decolour with Tonsil or carbon.In addition, method of the present invention has also been avoided the loss of OPA yield.
Compared with prior art, the feature of method of the present invention also is to have shortened the reaction times, thereby makes continuous processing become possibility.
Embodiment 1
Step a):
61g (0.25mol) tetrachloro-o-Xylol (TCX) (purity 99%) is introduced reactor, add 300g (5mol) acetate then.Slowly add the solution of 44g (1.1mol) NaOH and 198g deionized water afterwards.Reacting by heating mixture to 160 ℃, and keep this temperature 1h.Reaction pressure is 3.8-3.9bar.Then, reaction mixture is cooled to 40 ℃, and shifts out reactor (obtaining 606g (525mi) reaction soln).Get the 2ml sample, and it is analyzed.Analytical results: the thick OPA of 99.43GC area %.
Extract thick OPA:
At first the thick OPA solution of 606g is mixed with the 50ml deionized water, then with 93g MTBE extraction 4 times.Merge organic phase, under 400-415mbar and 34-72 ℃, in Rotavapor, concentrate then, pass through until no longer including fraction.Obtain the 54g residuum by evaporation.
Step b):
With the whole residuums and the 375ml methanol mixed of evaporation gained, add the dense H of 2ml
2SO
4So that pH is transferred to 0.5.After keeping 2 hours under 50 ℃, add the NaOH of 50% intensity of 10ml.Then reaction mixture is concentrated in Rotavapor, mix with the 175ml deionized water afterwards, and extract 3 times with 80ml MTBE down at 25 ℃.Merge organic phase, in Rotavapor, concentrate.Final weight is 42.4g.
It is 135-140 ℃ that thick acetal is carried out the distillatory bath temperature, and bottom temp is 113-114 ℃, and head temperature is 110-111 ℃.Pressure is 8-10mbar.Final weight: 41.2g OPA dimethoxy acetal (theoretical yield 91%).
Step c): decompose OPA dimethoxy acetal
200g OPA dimethoxy acetal is added in the 500g deionized water, and described deionized water is regulated pH to 2.0 with sulfuric acid, and pressure is reduced to about 150mbar.Begin heating then.When bottom temp is 53 ℃, when pressure is 155mbar, begins to collect fraction.Obtain the 270ml fraction altogether.Behind the 4h organic phase is carried out IPC-GC and analyze, show that OPA purity is 99.89 area %.
Add after the 500ml DIPE, extract OPA down at 50 ℃.After being separated, (each 100ml) washs organic phase 2 times with deionized water.With the light yellow organic solution reflux of having washed, under barometric point, remove residual water in the organic phase by component distillation.Obtain the water of 9.5ml altogether.
Subsequently, begin slowly to cool off.Under 42 ℃, OPA begins crystallization.Further it is cooled to 15 ℃.
By G-2frit crystalline OPA is leached, with 150ml DIPE washing and under 40-45 ℃ dry overnight in a vacuum.91.5g content is separated greater than 99.8% dry OPA and 450ml mother liquor.Theoretical yield is 61.5%.In the water and the water from washing that theoretical yield according to 100%, remaining OPA be present in mother liquor, obtained by decomposition, because the high purity and the light colour of solution, all these all can recycling in next acetal decomposition is handled.Therefore make quantitative acetal decomposition become possibility.